The present invention relates generally to control of vehicles, and more specifically to automatic control of vehicles such as aircraft by an independently operating computer system.
Limited control of vehicles such as aircraft has been known for some time. For example, autopilots are available which can maintain the current characteristics of an aircraft such as heading, airspeed, and altitude. Some autopilots can perform certain simple changes such as changing altitude while maintaining course and airspeed. This is accomplished by setting the autopilot to a new value, in this example a new altitude, and allowing it to "correct" to the new value. The autopilot operates as if the aircraft had suddenly changed from a currently programmed altitude to a new one, and the autopilot were trying to return to the original altitude.
Autopilots operate by controlling the various control surfaces of an aircraft, such as the rudder, ailerons, and flaps. The engine's throttle is also controlled to provide airspeed control. The autopilot operates on a feedback mechanism which causes adjustments to be made to the appropriate controllable function in order to bring the actual operating parameters in line with those which currently exist. For example, if the airspeed is lower than the desired value, the autopilot increases the throttle. If the altitude is too low, the autopilot increases it, generally by raising the flaps slightly and increasing the throttle to keep airspeed constant. These feedback controls are very simple in nature, and are hardwired into the autopilot.
The feedback controls used in standard autopilots are simple enough that they could be wired in an analog controllers, and this has in fact been done in the past. At the present time, however, digital computers are used to provide the desired control functions. These onboard computers monitor the current value of several variables which indicate the status of the aircraft, and signal changes in the appropriate aircraft controls when any of these variables change from the desired values. The nature of the changes are relatively simple, and are determined in advance for a particular aircraft design. Thus, all aircraft having the same design utilize the same programs for effectuating the autopilot functions.
The number of maneuvers which can be performed by current autopilot systems is extremely limited. They are capable of flying civilian or military aircraft under normal conditions and static plans. For example, if a pilot desired to continue straight and level flight for an extended period of time, an autopilot is the ideal tool, so long as unusual atmospheric conditions are not encountered. Simple, slow turns and altitude changes can be made by changing the appropriate settings on an autopilot. But difficult maneuvers, such as aerobatic maneuvers, are not possible using current automatic controllers.
It would be desirable for an automatic control system for vehicles such as aircraft to be able to undertake maneuvers which are much more complex than those just described. It would be desirable for these control systems to be under the constant control of the pilot under normal circumstances, but for them to be capable of independent operation in unusual situations, such as pilot incapacitation on military aircraft. It would be further desirable that the degree of independence of the automatic control systems be easily adjusted by the pilot.
In order to accomplish these and other objects, an expert vehicle control system suitable for use in vehicles such as aircraft provides several layers of control of the vehicle. A lowest level monitors the current state of the vehicle, and changes the appropriate vehicle controls to bring the vehicle to match selected goals. A higher level determines a series of intermediate goals which can be used to cause the lowest level controller to implement desired maneuvers. A decision-making level can be used to determine the appropriate maneuvers to be implemented in accordance with known conditions, such as mission plans.
The novel features which characterize the present invention are defined by the claims. The foregoing and other objects and advantages of the present invention will hereafter appear, and for purposes of illustration, but not of limitation, a preferred embodiment is described in conjunction with the drawings.